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A friend sent me two short clips with the first showing a regular light bulb that shines brighter when resistance decreases.

Then a LED which seems to act in the opposite way. Shining brighter with higher resistance.

It's powered by a 9V battery.

We couldn't figure out why the LED behaves this way.

Higher current should increase brightness, as far as I know. What are we missing?

Anyone that can enlighten us?

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    \$\begingroup\$ The intensity goes down again if you over drive. I suspect because it gets hot inside. \$\endgroup\$
    – Oldfart
    Apr 20, 2020 at 8:06
  • \$\begingroup\$ An LED generally shines brighter with more current goint through it, up to the point it becomes damaged. I haven't watched the video but maybe you can explain what they did there to cause this effect. It could be they operated the LED outside of its normal parameters. \$\endgroup\$
    – StarCat
    Apr 20, 2020 at 8:12

3 Answers 3

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I would say that since you applied 9V to a LED and reduced the series resistance to almost zero, you burned it. The light bulb though is behaving as expected. Try using another LED and add some additional series resistance to limit the maximum current, according to :

$$R_{limit} \approx \frac{9V-2V}{10mA}=700\Omega \approx 820\Omega$$

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  • \$\begingroup\$ Alright, thanks. I'll mark this as the correct answer since you were first. \$\endgroup\$ Apr 20, 2020 at 8:11
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Improper operation and usage of LED outside its safe operating parameters.

With too low resistance, it overheats and gets damaged.

Apparently when it cools down it seems to resume operating, but most likely it has already suffered some damage.

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  • \$\begingroup\$ Yeah I was going to say they are practically connecting the LED through some limiting resistance for normal operation. But then connect LED directly to power source with no limiting resistance to cause it to overheat and burn. Then at last minute, they disconnect it before it could totally destruct. It only becomes dim when it’s burning out and becoming somewhat damaged. \$\endgroup\$
    – Leoman12
    Apr 20, 2020 at 23:32
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Sorry, but the video lies. The backgrounds of the led placements are different, video camera makes the effect.

This video https://www.youtube.com/watch?v=CcG1bJc-dao&feature=youtu.be

proves only that video image brightness doesn't grow above the maximum which is reached already without the led.

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  • \$\begingroup\$ Well, he observed it, and then made a video out of the observation. I agree the background is pretty poor but the effect was still real. I think it has been answered above though. \$\endgroup\$ Apr 27, 2020 at 11:09
  • \$\begingroup\$ 2 incidents (=no intermediate steps and the bright background just behind the interesting point) make the video look it's made to present crap intentionally . Many free energy videos are more carefully made \$\endgroup\$
    – user287001
    Apr 27, 2020 at 12:20

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